Lightweight and corrosion-resistant nonmetal electrical conductors are desirable for applications in many industries, including, for example, the aerospace, electronics, medical device, and marine instrument industries.
Current electrical signal or power lines include copper and an insulating layer. Large diameter, highly dense copper cables, however, are relatively heavy, which is especially disadvantageous in aircraft containing miles of cables. In some transformer applications, aluminum, which is lighter than copper, has been used, but lighter and/or corrosive resistant materials are desirable.
Due to several attributes of carbon nanotubes (CNTs), such as their low density, one dimensional structure, tunable electrical properties, and/or high mechanical performance, various scales of CNTs and CNT assemblies have been studied for possible use in electrical conduction applications, including, for example, individual CNTs and macroscale CNT assemblies, such as yarns (i.e., fibers), sheets, and ribbons.
Although the electrical conductivity of an individual CNT can be as high as 106 S/cm for a single-wall CNT (SWNT), and 3.3×104 S/cm for a multi-wall CNT, macroscopic CNT assemblies have shown limited conductivity. Typically, CNT fibers have demonstrated better electrical performance than CNT sheets, which are required for scaled-up engineering applications, such as surfaces for aircraft fuselage and wind blades. For some CNT sheets, the electrical conductivity can be significantly reduced from about 104 S/cm to about 102 S/cm when the thickness of the sheet is increased from a nanometer scale to a micrometer or millimeter scale.
Other materials, such as iodine, have been added to CNT sheets in an effort to improve electrical conductivity. These other materials, however, typically have poor air stability and/or do not remain in place during the use of the CNT sheets.
There remains a need for composite materials that take advantage of the properties of carbon nanotubes, and are stable, scalable, lightweight, highly conductive, and/or capable of being produced with facile and/or scalable processes.